Prevention of infection with HIV-1 is a key goal of the HIV vaccine field. However, it is apparent that current vaccine candidates that elicit T cell immune responses may not provide sterilizing immunity. Rather these vaccines may be evaluated on their effects on post-infection secondary outcomes, such as plasma viral load of infected vaccines compared to recipients of placebo. A related goal for the field is the continued search for markers that might indicate the type of immune responses associated with protection from HIV-1 or modification of the course of viral replication. This project will evaluate the early viral and immunologic events following HIV-1 infection is a cohort of persons identified with recent HIV-1 infection in South Africa. Specific Aim 1 will measure the course of HIV-1 viral load and CD4 T cells counts, and describe HIV-related clinical events during the first 48 weeks following enrolment. Specific Aim 2 will determine whether subsets of HIV-1-specific CD4+ T cells defined by functional and phenotypic markers demonstrate resistance to infection with HIV-1 or alteration of permissiveness for HIV replication as demonstrated by quantification of intracellular HIV-1 DNA transcripts. Specific Aim 3 will correlate the course of HIV-1 viral load with populations of T cell functional profiles. Taken together, these data will provide preliminary data that will be useful in the planning of future vaccine trials. This includes characterization of viral dynamics and cellular responses to infection with the predominant viral subtype causing the global HIV-1 epidemic. The data will also provide preliminary evidence for in vivo differences in functional effect of CD4+ T cells of differing phenotypic and functional profiles. [unreadable] [unreadable] [unreadable]